// my_strlen    my_strcpy    my_strcat
#include<stdio.h>
int my_strlen(char*s)
{
	int count = 0;
	while (*s++!='\0')
	{
		count++;
	}
	return count;
}

char* my_strcpy(char*s3,char*s1,int sz1)
{
	char* ret = s3;
	while (*s3++ = *s1++);
	return ret;
}
void my_strcat(char*s1,char*s2,int sz1,int sz2)
{
	int i = 0;
	for (i = 0; i < sz2; i++)
	{
		*(s1 + sz1 + i) = *(s2 + i);
	}
}
int main()
{
	char s1[100] = "abcd";
	char s2[] = "efgh";
	char s3[100] = { 0 };
	int sz1 = my_strlen(s1);
	int sz2 = my_strlen(s2);
	printf("%d\n", sz1);
	printf("%s\n",my_strcpy(s3, s1, sz1));
	my_strcat(s1,s2,sz1,sz2);
	printf("%s\n", s1);
	return 0;
}